Self-Forming Microlenses For VCSEL Arrays

ABSTRACT

A Vertical Cavity Surface Emitting Laser (VCSEL) assembly including a VCSEL structure having a light-emitting region located on its surface, a relatively wettable region of a surface modifier coating formed over the light emitting region, and a microlens formed on the relatively wettable region. A relatively non-wettable region of the surface modifier coating is formed around the light-emitting region (e.g., on the electrode surrounding the light-emitting region). The surface modifier coating is formed, for example, from one or more organothiols that change the surface energies of the light-emitting region and/or the electrode to facilitate self-assembly and self-registration of the microlens material. The microlens material is printed, microjetted, or dip coated onto the VCSEL structure such that the microlens material wets to the relatively wettable region, thereby forming a liquid bead that is reliably positioned over the light-emitting region. The liquid bead is then cured to form the microlens.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/015,937, entitled “Self-Forming Microlenses For VCSEL Arrays” filedDec. 17, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to electronic materials processing, andmore particularly to a system and method for fabricating microlenses onVertical Cavity Surface Emitting Lasers (VCSELs).

2. Related Art

Unlike edge-emitting lasers that emit laser light horizontally from theetched side edge of a semiconductor stack, VCSELs are characterized inthat the emitted laser beam is emitted vertically from the substratesurface. VCSELs thus have significant advantages over edge-emittinglasers in the areas of lower manufacturing, packaging, alignment, andtesting costs, as well as lower power dissipation.

FIG. 8 is a perspective view depicting a multiple beam laser scanner orROS (raster output scanner) system 800 used, for example, in a highresolution, high speed printing apparatus. System 800 generally utilizesa two-dimensional VCSEL array 810 that transmits several light beams 815through pre-polygon optical devices 820 to a rotating polygonal mirror830, which scans the beams through scan optics 840 and a directingmirror 850 to a photo-receptor 860, which performs high speedprinting/scanning functions in response to the modulated intensity ofthe individual beams according to known techniques.

FIG. 9 is an enlarged plan view showing a thirty-six beam VCSEL array810A, which represents one type of VCSEL array utilized in systems suchas those depicted in FIG. 8. Each VCSEL 812 of array 810A is formed byan active region (e.g., GaAs) surrounded by an electrode (e.g., gold).In each VCSEL, laser photons resonate between mirrors grown into thesubstrate structure, and then emit vertically from light-emittingregions of the wafer surface.

Referring again to FIG. 8, in order for system 800 to operate asintended, the beams generated by array 810 must have sufficient energyto adequately expose the photoreceptor 860 or recording medium. That isif the light beams are too low in energy or power, then they will beunable to generate an image with enough light intensity that can bedetected, captured, or recorded by the photoreceptor or recordingmedium.

One approach to addressing this problem is to increase the intensitygenerated by each beam, and to increase the sensitivity of thephotoreceptor, thereby providing a suitable amount of light exposure.However, the beam intensity of current VCSEL devices is limited, anddriving the VCSELs harder with more current can adversely affectlifetime and single transverse mode emission characteristics.

Another approach to improving the throughput of the optical systemwithout changing the spacing between VCSELs is to utilize microlenses toreduce the divergence angle of the individual VCSELs in the array. Thisapproach allows more light to be captured by the optical system andtransmitted to the photoreceptor.

Current approaches to integrate microlenses and VCSEL arrays for thistype of purpose include the hybrid mechanical assembly of a VCSEL arrayand a separate microlens array, and forming microlenses on the VCSEL bydeposition and reflow of material like photoresist as additional stepsin the VCSEL array fabrication process. A problem with the firstconventional approach is that aligning the separate microlens array withthe VCSEL array is time consuming and tedious, and prone to alignmenterror that can greatly reduce the effectiveness of the lens array. Aproblem with the second conventional approach is that the additional isthat the additional processing steps significantly increase fabricationcosts.

What is needed is an efficient and reliable method for formingmicrolenses on VCSEL arrays that avoids the problems associated with theconventional approaches discussed above.

SUMMARY OF THE INVENTION

The present invention is directed to a VCSEL (or other light emitting orlight receiving device) assembly and a method for producing VCSELassemblies in which VCSEL (or other light emitting or receiving)structures are surface-treated in a way that causes an appliedlens-forming material to form self-assembled and self-registered(self-aligned) microlens structures over the light-emitting region ofeach VCSEL. In particular, the surface treatment involves forming asurface modifier coating (e.g., reactive organic molecules or polymers)over the VCSEL light-emitting region such that a liquid lens-formingmaterial that is deposited onto the surface can be confined to thatregion, thus forming a domed liquid bead over the light-emitting region.The domed liquid bead may then be cured to fix the position, shape, andstructure of the self-assembling microlens. As in conventional systems,the presence of the microlens over the VCSEL reduces the divergenceangle of the laser (light) beam generated from the VCSEL withoutincreasing the size (area) of the light-generating region, therebyfacilitating the formation of closely-spaced VCSEL arrays. The presentinvention thus provides advantages over conventional microlens formingmethods by providing self-assembly and self-alignment(self-registration) of the microlenses, which avoids the cost andassembly difficulties associated with the integration of a VCSEL Arrayand a microlens array, as required by conventional microlens formationtechniques.

In accordance with an exemplary embodiment, a microlens is formed on aVCSEL utilizing GaAs as the active material, and a gold electrode thatis formed on an upper GaAs surface and defines a central aperture thatsurrounds a light-emitting region. Surface treatment involves forming arelatively wettable monolayer region over the light-emitting region, andforming a relatively non-wettable monolayer region on the electrodearound the relatively wettable monolayer region. In one embodiment, boththe relatively wettable and relatively non-wettable monolayer regionsare formed using appropriate organothiols (e.g., an organothiolfunctionalized with a carboxylic acid to form the relatively wettableregion, and an alkanethiol to form the relatively non-wettable region).Both of these monolayer regions may be formed by dip-coating, thusfacilitating use of the present invention to perform low-cost“retrofitting” of microlens structures onto existing VCSEL arrays. Inother embodiments only one region may be modified using a chemicalmodifier. After forming the monolayer regions, a lens-forming material(e.g., optical epoxy or polymer) is printed, microjetted, or dip coatedonto the VCSEL surface. The lens-forming material is either applied as aliquid, or as a solid that is subsequently melted. The liquid materialself-registers to the relatively wettable monolayer region (i.e., flowsout of the relatively non-wettable region), thus forming a domed liquidbead over the light-emitting region. The liquid bead is then cured orotherwise solidified to form the desired microlens.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a perspective view showing a VCSEL assembly according to anembodiment of the present invention;

FIG. 2 is a flow diagram showing a simplified method for producing VCSELassemblies according to another embodiment of the present invention;

FIG. 3 is a top view showing a VCSEL array prior to the formation of asurface modifier coating and microlens;

FIGS. 4(A) and 4(B) are cross-sectional views showing the VCSEL array ofFIG. 5 during the formation of a surface modifier coating;

FIG. 5 is a top view showing the VCSEL array of FIG. 3 after formationof a surface modifier coating and microlens;

FIGS. 6(A) and 6(B) are cross-sectional views showing the application oflens-forming material onto the VCSEL array of FIG. 3 according toalternative embodiments of the invention;

FIGS. 7(A) and 7(B) are perspective views showing the application oflens-forming material onto the VCSEL array of FIG. 3 according toanother alternative embodiment of the invention;

FIG. 8 is a simplified perspective view showing a conventional multiplebeam laser scanner system; and

FIG. 9 is an enlarged plan view showing a conventional thirty-six beamVCSEL array.

DETAILED DESCRIPTION

The present invention is described below with particular reference toVertical Cavity Surface Emitting Laser (VCSEL) devices, and inparticular to low-cost VCSEL assemblies that include a microlens formedover each VCSEL device. While the present invention is described belowwith particular reference to VCSEL devices utilizing gallium-arsenide(GaAs) as an active material, and gold (Au) for electrodes, it should beappreciated that the present invention is applicable to VCSEL devicesconstructed using other active materials and electrode metals. Inaddition, positional terms such as “upper”, “lower”, and “over” are usedherein for convenience to indicate relative positions of associatedstructures formed on the subject VCSEL assembly, and are not intended tobe related to a fixed external reference. Further, the same techniquesand methods described herein can be applied to other light emittingstructures, such as single light emitting diodes (LEDs), one-dimensionallinear LED arrays, and two-dimensional LED arrays, and light receivingstructures, such as image sensors (light emitting structures and lightreceiving structures are herein collectively referred to as “lightemitting/receiving structures”).

FIG. 1 is a simplified, partially exploded perspective view showing aVCSEL assembly 100 formed in accordance with an embodiment of thepresent invention. Referring to the left side of FIG. 1, VCSEL assembly100 generally includes a VCSEL structure 110 including an upperelectrode 120, a surface modifier coating 130 formed over upperelectrode 120, and a microlens 140 formed on surface modifier coating130.

VCSEL structure 110 generally includes a substrate 112 (e.g., n-dopedGaAs), a first reflector stack 112 (e.g., alternating layers of n-dopedGaAs and aluminum arsenide (AlAs)) formed over substrate 112, an activeregion 113 formed over first reflector stack 112, and a second reflectorstack 114 (e.g., alternating layers of p-doped GaAs and AlAs) formedover active region 113. Upper electrode 120 is formed on an uppersurface 116 of VCSEL structure 110, and a lower electrode 125 is formedon a lower surface of substrate 111. Typically, electrodes 120 and 125include one of gold (Au) titanium, platinum and nickel. Upper electrode120 defines a central aperture 122 the surrounds a light-emitting region118 of upper surface 116. In general, during operation, a voltagepotential applied across electrodes 120 and 125 generates laser photonsat a frequency defined by the material and arrangement of VCSELstructure 110, which produces a laser beam LG that is emitted throughlight-emitting region 118 of upper surface 111. Note that additionalstructures associated with the operation of conventional VCSEL devices(e.g., cladding layers provided between active region 116 and thereflector stacks) are not required to describe the present invention,and are therefore omitted for brevity.

In accordance with an aspect of the present invention, surface modifiercoating 130 is formed on upper surface 111 and/or upper electrode 120 tochange the surface energy of the GaAs/metal in a manner that facilitatesthe self-assembly and self-registration of liquid lens-forming material,thereby facilitating the self-registration and self-assembly ofmicrolens 140 over light-emitting region 118. In one embodiment, surfacemodifier coating 130 includes a relatively wettable region 132 that islocated over light-emitting region 111, and a relatively non-wettableregion 134 located around relatively wettable region 132. The terms“relatively wettable” and “relatively non-wettable” are utilized hereinto describe surface energies that respectively cause a given liquid tospread or ball up. For example, wetting (or “relatively wettable”) meansthat the contact angle between the liquid and the solid surface is small(e.g. <90°) that the liquid spreads over the solid surface easily, andnonwetting (or “relatively wettable”) means that the angle is largerthan that of the wettable region (e.g. >90°) so that the liquid has atendency to preferentially coat the wettable region. In someembodiments, it may be preferable that the surface modifier coating onthe light-emitting region 118 be non-wettable and the outlying regionwettable. With respect to water, “relatively wettable” is synonymouswith the term “hydrophilic”, and “relatively non-wettable” is synonymouswith “hydrophobic”. As described below, with this arrangement aliquid-lens forming material applied onto surface modifier coating 130forms a dome-shaped (domed) liquid bead on relatively wettable region132 and flows away from relatively non-wettable region 134, which isthen cured to form desired microlens 140. By positioning relativelywettable region 132 over light-emitting region 118, the presentinvention facilitates the self-registration (self-alignment) ofmicrolens 140 over light-emitting region 118 due to the propensity forthe applied lens-forming material to spontaneously generate a domedliquid bead on relatively wettable region 132. Further, by shapingrelatively wettable region 132 in a circular shape and by selecting asuitable lens-forming material (i.e., a material that, in liquid form,generates a desired dome-shaped curvature), the present invention alsofacilitates self-assembly of microlens 140. This microlens is formedwith good registration to the underlying light emitting region.

In accordance with another aspect of the present invention, relativelywettable region 132 and relatively non-wettable region 134 form aperipheral boundary, and microlens 140 has an outer peripheral edge thatis substantially aligned with this peripheral boundary. As mentionedabove, the liquid lens-forming material forms a domed liquid bead thatis self-aligned with relatively wettable region 132. The term“substantially aligned” is used herein to account for slightdisplacement of the outer edge of microlens 140 relative to theperipheral wettable/non-wettable boundary that may occur during curing(i.e., expansion or contraction of the solidifying lens material).Referring to FIG. 1, in a presently preferred embodiment, a peripheralboundary 135A is defined by aperture 122 of upper electrode 120 (i.e.,relatively wettable region 132 is located inside aperture 122, andrelatively non-wettable region 134 is located outside of aperture122—e.g., above upper electrode 120), and a microlens 140A has an outeredge 145A that is substantially aligned with peripheral boundary 135A.In another embodiment, which is indicated by dashed lines in FIG. 1, aperipheral wettable/non-wettable boundary 135B may be formed over upperelectrode 120, and an associated microlens 140B having an outer edge145B that is substantially aligned with peripheral boundary 135B.Alternatively, a peripheral wettable/non-wettable boundary 135C may beformed outside the outer edge of upper electrode 120, and an associatedmicrolens 140C may be formed that includes an outer edge 145Csubstantially aligned with peripheral boundary 135C. Moreover, althoughthe presently preferred assembly a includes surface modifier coating 130having both relatively wettable region 132 and relatively non-wettableregion 134, one of these regions may be omitted if the correspondingsurface/electrode exhibit suitable surface energies. For example, iflight-emitting region 118 has a surface energy exhibiting a suitablewettability to the selected lens-forming material, then wettable region132 may be omitted (i.e., surface modifier coating 130 includes onlyrelatively non-wettable region 134). Alternatively, if upper electrode120 has a surface energy exhibiting a suitable non-wettability to theselected lens-forming material, then non-wettable region 134 may beomitted (i.e., surface modifier coating 130 includes only relativelywettable region 132).

In accordance with an embodiment of the present invention, surfacemodifier coating 130 is a self-assembled monolayer (SAM) consisting ofat least one organothiol. Organothiols (RSH) form SAMs on GaAs, theactive material of VCSEL structure 110, and also on Au, the metaltypically used for upper electrode 120. SAMs can be applied selectivelyAu and GaAs surfaces because the thin native oxide on GaAs is relativelyunreactive towards organothiols. Because of this selectivity, thewettability of the surfaces of Au and GaAs can be changed selectivelythrough the use of appropriate organothiols, e.g., an alkanethiol isrelatively non-wettable (hydrophobic) and can thus be used to formrelatively non-wettable region 134 of surface modifier coating 130,while a many functionalized organothiols, e.g., an organothiol with achemically polar headgroup such as carboxylic acid terminated-thiol, isrelatively wettable (hydrophilic), and can thus be used to formrelatively wettable region 134. SAMs formed of organothiols includingsulfur, oxygen, and carbon may also be formed on Au and GaAs, with thepresence of sulfur-based SAMs being relatively easy to detect. Othermaterials such as thiol-functionalized polymers can also be used assurface modifiers.

According to another aspect of the present invention, microlens 140 isformed using an optical pre-polymer or an optical polymer. The terms“optical pre-polymer” and “optical polymer” are used herein to indicatematerials that are either a substantially transparent liquid at thewavelengths of interest or a solid material that forms a substantiallytransparent liquid upon melting, and in either case forms asubstantially transparent solid microlens structure at the wavelengthsof interest after a suitable curing process. Other suitable materialsthat exhibit the characteristics of optical pre-polymers and opticalpolymers may be used as well. In these cases the surface modifier formsa thin coating on the surface (<100 nm) that comprises more than onemonolayer.

FIG. 2 is a flow diagram showing a simplified production method forgenerating VCSEL assembly 100 according to another embodiment of thepresent invention. FIGS. 3 through 7 depict exemplary stages of theproduction method.

Referring to the upper portion of FIG. 2, the production method beginsby fabricating a VCSEL structure using known techniques such that theVCSEL structure includes a light-emitting region located on an uppersurface thereof (block 210). As discussed above, in one embodiment, anupper layer 114 of VCSEL structure 110 includes GaAs, such that an uppersurface 116 of VCSEL structure 110 includes GaAs. In addition, upperelectrode 120 is formed on upper surface 116 in the manner describedabove (i.e., such that an aperture 122 surrounds a light-emitting region118 of VCSEL structure 110.

FIG. 3 is a top view showing a simplified VCSEL array 110-1 thatincludes two VCSELs, and is utilized to illustrate exemplary embodimentsof the present invention. Each VCSEL device includes an electrode 120and a light-emitting region 118 formed on an upper surface 116. VCSELarray 110-1 may include any number of VCSEL structures.

According to the present invention, the upper surface of the VCSELstructure is processed to form a surface modifier coating that includesat least one of relatively wettable region located over thelight-emitting region, and relatively non-wettable region surroundingthe light-emitting region (FIG. 2, block 220). As indicated in FIGS.3(A) and 3(B), in one embodiment the surface modifier coating is formedin a two phase process that involves exposing VCSEL array 110-1 to afirst thiol 410 (e.g., R-SH) to form relatively non-wettable SAM(region) 134 of the surface modifier coating on electrodes 120 (FIG.3(A)), and then exposing VCSEL array 110-1 to a second thiol 420 (e.g.,R′-SH in dilute NH₄OH) to form relatively wettable SAM (region) 132 ofthe surface modifier coating over light-emitting region 118 (FIG. 3(B)).Note that, in the present context, the “upper surface” is intended toinclude both upper surface 116 and the exposed surface of electrode 120.Note also that exposed portions of upper surface 116 located outside ofthe region defined by upper electrodes 120 may form relatively wettableSAMs without a debilitating effect. In this manner, the upper surface ofVCSEL array 110-1 is treated in a way that produces areas of differentwettabilities than enable self-assembly and self-alignment of themicrolens structure.

Next, lens-forming material is deposited over the surface of the VCSELstructure such that the lens-forming material forms a domed liquid beadover the relatively wettable region (FIG. 2, block 230), and the domedliquid bead is cured (if necessary) to form the completed microlens(FIG. 2, block 240). As indicated in FIG. 5, after upper surface 116 ofVCSEL array 110-1 has been appropriately treated to provide relativelywettable regions 132 over light-emitting regions 118 and relativelynon-wettable regions 134 over electrodes 120, a lens-forming material(e.g., a photo or thermally cured optical epoxy or polymer, such asNorland optical adhesive) 510 is then deposited using micro-jetting,printing, dip-coating, or another suitable method and optionally curedto form microlenses 140.

FIG. 6(A) is a side view showing a first example in which a liquidlens-forming material 510-1 is applied (deposited) onto VCSEL array110-1 by micro-jetting (i.e., ejecting from a print head similar tothose used in ink-jet printers). The spreading of the uncuredlens-forming material is controlled by the wettability of the SAMsprovided in relatively wetting region 132 and relatively non-wettingregion 134. That is, due to the wetting characteristic of the SAMprovided in relatively wettable region 132, the liquid lens-formingmaterial 510 entering aperture 122 forms a self-aligned domed liquidbead 510-1A that can be subsequently cured (if necessary) to formmicrolens 140. In contrast, the control provided by thewetting/non-wetting surfaces helps correct for mis-registration ofprinted drops. For example, a mis-registered uncured drop 510-1B willflow out of the region located over electrode 120 due to surfacetension. Thus, the applied liquid microlens material 510 becomesself-aligned over light-emitting region 118, and forms a domed beadstructure on the relatively wettable region.

FIG. 6(B) depicts a second method for forming microlenses in which asolid lens-forming material 510-2 is printed in a solid form overaperture 122, and then melted to form a domed liquid bead 510-2A, whichis in turn cured or otherwise allowed to solidify to form microlens 140.Note again that, when melted, the liquefied lens-forming materialself-registers to relatively wettable region 132 (i.e., flows away fromrelatively non-wettable region 134), and self-assembles in that it formsdomed liquid bead 510-2A.

FIGS. 7(A) and 7(B) are perspective views showing yet another method fordepositing lens-forming material on VCSEL array 110-1 using dip-coating.Referring to FIG. 7(A), a vat or tank 710 includes a first liquid (e.g.,water) 720 with a liquid lens-forming material layer (e.g., polymer) 730floating thereon. In one embodiment, when VCSEL array 110-1 is insertedinto tank 710 in the direction indicated by arrow A and passed throughliquid lens-forming material layer 730. As shown in FIG. 7(B), VCSELarray 110-1 then passes from liquid lens-forming material layer 730 intofirst liquid 720. During this process, drops of liquid lens-formingmaterial adhere to the region 132 formed over light-emitting regions 118that has been treated with a surface modifier that is poorly wetted byliquid one. While immersed in liquid one, ultraviolet rays UV areapplied to cure the drops of liquid lens-forming material, therebyforming microlenses 140.

The VCSEL production method described herein is capable of producingsingle VCSELs, one-dimensional linear VCSEL arrays (e.g., VCSEL array110-1) and two-dimensional arrays of VCSELs with microlenses. Further,the proposed process is separable from the VCSEL manufacturing process,which enables the “retrofitting” fabrication of microlenses on completedVCSEL wafers or pre-fabricated VCSEL devices. That is, because theproduction method of the present invention does not require traditionalmicro-processing, minimal process integration with existing VCSELfabrication processes is necessary. Microlenses can be easilyretrofitted onto pre-fabricated VCSELs obtained from various producers.For example, microlenses can be fabricated by simply dipping completedVCSEL wafers into solutions of chemicals. The process is also very fast,with the formation of the SAMs taking seconds, and the formation of themicrolens taking mere minutes (e.g., for UV-cure epoxies). Thisself-assembly and self-registration technique is a rugged, low costprocess similar to how immersion gold is applied to pads on cheapcircuit boards. The present invention thus provides the advantage ofself-assembly and self-alignment of the microlenses and avoids the costand assembly difficulties associated with the integration of a VCSELArray and a microlens array. VCSEL/Microlens arrays produced in theproposed manner are thus more robust, and less expensive to produce.

The microlenses produced in accordance with the present invention reducethe divergence angle of each VCSEL while leaving the distance betweenVCSELs in the array unchanged. This keeps the magnification of theoptical system and therefore the input acceptance angle of the opticalsystem unchanged. Therefore, more light from the VCSEL array is capturedby, for example, the ROS optics and transmitted to the photoreceptor inhigh-resolution laser scanner/printer systems. Much of the accuracyrequired for the microlens formation and positioning is already providedby the VCSEL structure, which is lithographically defined. Laserscanners will have their throughput increased and not be subject to thetypes of variations associated with misalignment of the microlensesrelative to the VCSEL emitters that occur during operation due tothermal expansion in the supporting mechanical structure.

Although the present invention has been described in connection withseveral embodiments, it is understood that this invention is not limitedto the embodiments disclosed, but is capable of various modificationsthat would be apparent to one of ordinary skill in the art. For example,the present invention may also be utilized in the production ofbackside-emitting VCSELs and intra-cavity VCSELs. In these devices, the“top” electrodes have no annular hole for light emission. Instead, lightis emitted from a light emitting region of the substrate side, where acommon cathode may or may not be situated. Similar to top-emittingVCSELs (such as those described above), the substrate surface on whichthe microlens would be made is typically GaAs. In embodiments wherethere is a common cathode, the cathode would have openings for light tocome out, so the microlens fabrication process would be nearly identicalto that described in detail above for the top-emitting case. Inintra-cavity VCSELs where both electrodes are situated on the topsurface, the backside would normally have no metal. In the laterembodiments, an additional step to pattern a backside metal would beneeded prior to microlens formation. Moreover, in addition to being usedin the production of VCSELs, the present invention may also be utilizedto produce other light sources, such as LEDs, and light receivingstructures, such as image sensor arrays. Therefore, the invention islimited only by the following claims.

1. A method for producing a Vertical Cavity Surface Emitting Laser(VCSEL) assembly, the method comprising: forming a VCSEL structureincluding having a light emitting region located on a surface of theVCSEL structure; processing the surface to form a surface modifiercoating including at least one of a relatively wettable region locatedover the light emitting region, and a relatively non-wettable regionsurrounding the light emitting region; and depositing a lens-formingmaterial over the surface such that the lens-forming material forms adomed liquid bead over the relatively wettable region.
 2. The methodaccording to claim 1, wherein processing the surface comprises forming arelatively non-wettable region surrounding the relatively wettableregion such that an interface between the relatively non-wettable regionand the relatively wettable region form a peripheral boundary.
 3. Themethod to claim 1, wherein forming the surface modifier coatingcomprises forming a self-assembling monolayer (SAM) consisting of atleast one organothiol.
 4. The method to claim 1, wherein forming themicrolens comprises at least one of printing, microjetting, and dipcoating the lens-forming material onto the relatively wettable region,and curing the domed liquid bead.
 5. The method to claim 4, whereinforming the microlens comprises printing the lens-forming material in asolid form, and further comprises melting the lens-forming material toform the domed liquid bead.
 6. The method to claim 4, wherein formingthe microlens comprises depositing one of an optical epoxy and anoptical polymer onto the relatively wettable region.
 7. The method toclaim 1, wherein forming the VCSEL structure comprises forming anelectrode on the surface such that the electrode defines an aperturesurrounding the light emitting region, and wherein processing thesurface comprises forming the relatively wettable region inside thecentral aperture defined by the electrode.
 8. The method to claim 7,wherein processing the surface further comprises forming the relativelynon-wettable region on the electrode such that the relativelynon-wettable region is located outside of the central aperture andsurrounds the wettable region.
 9. The method to claim 7, wherein formingthe surface modifier coating comprises forming a self-assemblingmonolayer (SAM) consisting of at least one organothiol.
 10. The methodto claim 9, wherein forming the surface modifier coating furthercomprises at least one of printing, microjetting, and dip coating the atleast one organothiol onto at least one of the light-emitting region andthe electrode.
 11. The method to claim 10, wherein forming the microlenscomprises at least one of printing, microjetting, and dip coating thelens-forming material onto the relatively wettable region, and curingthe domed liquid bead.
 12. The method to claim 11, wherein forming themicrolens comprises printing the lens-forming material in a solid form,and further comprises melting the lens-forming material for form thedomed liquid bead.
 13. The method to claim 12, wherein forming themicrolens comprises depositing one of an optical epoxy and an opticalpolymer onto the relatively wettable region.
 14. The method according toclaim 1, wherein depositing the lens-forming material comprisesinserting the VCSEL structure into a vat, the vat containing a firstliquid and a liquid lens-forming material layer floating on the firstliquid, such that the VCSEL structure passes through the liquidlens-forming material layer and into the first liquid, and wherein themethod further comprises curing a drop of said liquid lens-formingmaterial, which forms said domed liquid bead over the relativelywettable region, while the VCSEL structure is submerged in the firstliquid.
 15. A method for forming microlenses on a light emittingstructure, the light emitting structure including having a lightemitting region located on a surface of the light emitting structure,the method comprising: processing the surface to form a surface modifiercoating including relatively wettable region located over the lightemitting region; and depositing a lens-forming material over the surfacesuch that the lens-forming material forms a domed liquid bead over therelatively wettable region.